Axial pin locks are frequently employed to secure objects such as vending machines to prevent unauthorized access. An axial pin lock provides a simple mechanical lock for securing each machine, resulting in a series of locks for a route of machines; the route attendant servicing the machines is provided with a matching series of keys.
FIG. 1 illustrates one example of a prior art key 10 for opening a tubular axial pin lock (not shown) to obtain access to a locked storage container such as a vending machine to be serviced to collect money and replenish the items to be sold. Examples of such locks where the lock pins are arranged in a circular pattern are taught in U.S. Pat. Nos. 4,716,749 and 5,018,376. The key 10 for such a lock has a hollow base member 12 that is generally cylindrical, and has a key indexing element 14 that is formed by an inwardly-extending tab. The base member 12 is machined to provide an array of grooves 16 having varying depths, each terminating at an activation surface 18 at a specified distance from a front surface 20 at which the groove 16 terminates, the position of the activation surface 18 defining the depth of the groove 16. The base member 12 is affixed to a handle 22.
In use, the base member 12 is aligned with the lock to allow the key indexing element 14 to slidably engage a matching recess in the lock. This alignment serves to properly orient the grooves 16 so as to align them with lock pins (not shown). The base member 12 is then inserted into the lock, bringing each of the activation surfaces 18 into forcible engagement with the corresponding lock pins of the lock. Each of the activation surfaces 18 pushes the lock pin against the pressure of a bias spring to a position corresponding to the depth of the groove 16, the depths of the grooves 16 being milled to bring all the lock pins to a position to form a shear plane to allow rotation of a cylinder of the lock to open the lock.
One alternative configuration for an axial pin lock has the lock pins are arranged in rows, such as taught in U.S. Pat. No. 4,446,709. FIG. 2 illustrates another prior art key 50, which is functionally similar to the key 10 but which is designed for use with an axial pin lock where the lock pins are arranged in a rectangular, rather than circular, configuration. The key 50 again has a base member 52 that is milled to provide an array of grooves 54, each terminating at activation surfaces 56, but does not have a separate indexing element since the rectangular form of the base member 52 can serve to properly align the grooves 54 with the lock pins. For some locks, one of the ends of the rectangle may be modified to provided a contoured end 58 to assure that, when the base member 52 is inserted into the lock, the grooves 54 align with the lock pins.
Locks and keys such as discussed above provide an inexpensive and reasonably secure system for limiting access to a number of locked storage containers. However, this system requires the user to carry a large number of keys, which can be unwieldy if a large number of locks are employed. This problem is exacerbated for service technicians who may need to service machines belonging to more than one service route. Furthermore, this system is susceptible to illicit access by a dishonest keyholder, such as employee theft.
More secure locks can be provided by using any of a variety of lock and key systems that employ smart locks to limit access to the locked containers and a single electronic key which can be programmed to open a number of locks, such as taught in U.S. Pat. Nos. 5,552,777; 5,745,044; 6,082,153; 6,384,711; 6,474,122; 6,552,650; and 6,615,625. These systems can also limit the window of access to a particular vending machine, and can provide a record of the history of which locks have been opened with a particular key and or which keys have been used to open a particular lock; this information can help identify losses due to dishonest key holders. While such systems provide security advantages, the costs of the smart locks are high. This becomes a severe cost burden for uses where a large number of locks must be employed. In the case of vending machine systems, the high cost of purchasing such smart locks is frequently prohibitive for the vendor who distributes goods through routes having a large number of vending machines.